1. Field of the Invention
The present invention is directed to transferring subscriber records and, as needed, messages for subscribers from one information services system to another and, more particularly, to performing such a transfer when each information services system operates on a local area network servicing tens of thousands or hundreds of thousands of subscribers.
2. Description of the Related Art
It has been become increasingly common, particularly in North America, for telephone companies to provide information services, such as voicemail, to subscribers. Examples of systems which enable public telephone companies to provide such services are described in U.S. Pat. Nos. 5,029,199; 5,193,110; and 5,260,990, all of which are assigned to the assignee of this application and are incorporated herein by reference. The systems are connected to a central office of a local telephone company or to a private branch exchange or other system handling calls for a large number of telephones When one of the telephones serviced by the central office or other system is not answered, the calling party is given an opportunity to leave a telephone message which is stored for later reproduction by the user of the called telephone. The mailbox owner is given the ability to reproduce, store or dispose of the messages in his or her voice mailbox.
Several of these information services systems may be connected at various nodes in a telephone network. The nodes may be all within a single local telephone company, or in several different local telephone companies, such as those within one or more of the regional Bell companies. Although these systems are designed to be easily expandable, the great popularity of the services provided, particularly voicemail, has required the installation of additional information services systems to service areas previously serviced by a single system. When the new system is installed, it is desirable to distribute the work done by old and new systems until they carry about the same load. Conventionally, a bulk transfer is used with removable media, such as magnetic tape, or via a direct connection between the two information services systems.
There are several drawbacks to using a bulk transfer to redistribute the subscriber data from one information services system to another. Scheduling a bulk transfer can be difficult, since a bulk transfer may cause a large load on system resources and at least the old system should be able to be used by subscribers during the transfer. Existing systems have such a large number of subscribers that it is very difficult, if not impossible, to prevent bulk transfers from impacting on the ability of the old information services system's ability to perform normal functions. It may even be necessary for the new and old information services systems to be out of service for a significant period of time during the transfer of data; although if magnetic media, such as tape, is used, the systems may be out of service at different periods of time.
Another problem with bulk transfers is the potential for loss of data or disruption of service for subscribers. For example, assume subscriber data on the old system are copied to a tape which is physically transported to the new system. Any messages left for the subscribers whose data are stored on the tape between the time that the data are copied and the new system begins taking messages for the subscribers, will be lost. Even if a bulk transfer is performed directly, e.g., via a wide area network (WAN), messages can be lost due to the lag between transfer of data and switching of service for a subscriber from the old system to the new system The only way to prevent lost messages in a bulk transfer method is to suspend service for the subscribers who have data being transferred This is an undesirable solution, since it may take many hours to create a tape, physically transport the tape to the new system, load the new system with data and switchover responsibility for handling the subscribers.